Processing facilities and other facilities routinely include tanks for storing liquids or other materials. For example, storage tanks are routinely used in tank farms and other storage facilities to store oil or other materials. As another example, oil tankers and other transport vessels routinely include numerous tanks storing oil or other materials. Processing facilities also often include tanks for implementing industrial processes.
Often times, it is necessary or desirable to measure the amount of material stored in a tank. This may be useful, for example, during loading of material into the tank or unloading of material from the tank or during liquid stock accounting. As a particular example, “legal metrology” often requires highly accurate measurements from a level sensor installed on the roof of a tank, such as during custody transfers or when levying taxes or duties. In bulk storage tanks, an error of one millimeter in a level reading can correspond to several cubic meters of volumetric error. This can result in losses of thousands of dollars for one or more parties. Moreover, this can have negative effects on stock reconciliation, which involves attempting to track where materials are located and how materials are lost.
Radar sensors are one type of sensor commonly used in various industries to measure material levels in tanks. A radar sensor transmits electromagnetic pulses towards material in a tank (possibly through a physical waveguide), and the pulses are reflected at different points including a surface of the material. The radar sensor uses time-of-flight calculations with the pulse reflections to measure a distance to the material. Radar sensors can also be used in multiple-material applications, such as with oil and water mixtures to measure distances to the oil surface and to the water surface underneath the oil. Other types of sensors can also be used to measure material levels in single-material or multiple-material applications.